furqan-lint is an open-source structural-honesty linter for Python, Rust, and Go. It catches a class of bug that ruff and mypy do not: the bug where a function declares it returns a string and its substrate sometimes returns None, the bug where a refactoring renames a public function and three enterprise customers' imports break in production, the bug where a function declares it returns an integer and its body has zero return statements anywhere. Five static checks ship in the current release: D24 (all-paths-return), D11 (status-coverage on Optional and Result and (T, error) producers), R3 (zero-return / ring-close), return-None mismatch, and additive-only public-surface diff. Together with ruff and mypy, the three tools form a three-layer pre-commit stack each layer of which catches what the previous layers cannot. This thesis paper is the technical specification: identity and purpose, the structural-honesty gap with primary-source verification, theoretical grounding in the Furqan programming language primitives (zahir/batin types, additive-only modules), the five checkers in detail, three-language implementation (Python via the built-in ast module, Rust via tree-sitter-rust, Go via a custom goast binary compiled at install time), the audit-of-self pattern with three documented failure modes, the empirical trajectory across twenty-seven versions and twenty-three audit rounds, the thirteen quality gates that catch what individual reviewer vigilance cannot, validation methodology, the reciprocal contract under tool-on-itself recursion, limitations, application-fit profile, and code and data availability. The tool ships across three languages: Python with full coverage, Rust with D24/D11/R3 via the rust optional dependency extra, and Go with D24/D11/additive via the go extra (Go 1.21+ toolchain required at install time for the goast binary to compile). It runs as a command-line program, as a pre-commit hook, and as a continuous-integration GitHub Action that adds three lines to a workflow file. Published on PyPI as furqan-lint and licensed under Apache 2.0; this paper is licensed under CC BY 4.0. furqan-lint is the operational instance of The Bayyinah Audit Framework v3.0 (Arfeen 2026i), the engineering discipline under which the tool was built, and is the engineering substrate that supported development of the Furqan programming language (Ashraf and Arfeen 2026), the Bayyinah Integrity Scanner (Arfeen 2026b, 2026c), and ten further companion publications under the BayyinahEnterprise research program. The framework made executable runs at tryfurqan.com; the project home is bayyinah.dev. Source repository: github.com/BayyinahEnterprise/furqan-lint. PyPI release: pypi.org/project/furqan-lint/ (v0.8.5).
Bilal Syed Arfeen (Mon,) studied this question.